amines Flashcards
(14 cards)
aliphatic
non aromatic
aromatic referring to
- planar
- cyclic
- stable due to delocalisation
how do you classify amines
depends on how many alkyl groups bonded to the n
a primary amine will have RNH2
a secondary amine will have RRNH
a tertiary amine will have RRRN
all of the Ns above still have their lone pair
a quaternary ammonium ion has the N bonded to 4 groups. it has a positive charge
why are quatnery ammonium ions not classed as amines
they have no lp on the N. the chemistry of the amines is drive by the lp on the N
how can you make aliphatic amines
- Nucleophilic substitution with h alkane and ammonia
- if you want a primary amine you have excess ammonia to minimise further substitution since the product (amine) is also a nucleophile
- if you want a quaternary ammonium salt you have excess h alkane to maximise further substitution
- not the preferred method because impure product - Reduction of nitriles
- nitrile can be gotten by nucleophilic substitution of h alkanes and cyanide ion, :CN-
How can you reduce nitriles to aliphatic amines
- Reduction with LiAlH4
RCN + [H] –> RCNH2 - Catalytic hydrogenation with H2 and nickel catalyst and heat
- also the conditions for nitrobenzene to phenylamine
How can you form aromatic amines
Reduction of nitrobenzene
1. Catalytic hydrogenation with H2 and nickel catalyst and heat. Forms water as well
- Reduction with Sn and HCl. Followed by NaOH. Forms water as well
Use of quaternary ammonium ions
Cationic surfactants (need anion)
Surfactants decrease the surface tension between two liquids or things in diff phases eg oil and water
When the quaternary ammonium salt has long alkyl groups, these alkyl chains are hydrophobic
The ionic N part is hydrophilic
So allows water and grease to mix
Used as detergent
Use of phenyl amines
Miss says used in the manufacture of dyes
Ms came across says :
making dyes
making quaternary ammonium salts
making (cationic) surfactants
making hair conditioner
making fabric softener
making detergents
Strongest imfs between amine molecules
H bonding
Bonded to very electronegative O, N or F
When drawing:
- 180 degree h bond. The h bond is the h, the n it’s attracted to on diff molecule and the n it’s bonded to
- lps
- delta charges
-
Why are amines bases
Why type of bases are they
What does their base strength depend on
LP on the N can for coordinate bond to H+, therefore they can act at BL bases: proton acceptors.
They are weak bases
Their bases strength depends on the availability of the lone pair
What will make the lp on the n of amines more or less available (therefore a stronger or weaker base)
More alkyl groups increases the e- density around the N because they are electron releasing so there is the inductive effect, a local change in the E distribution
so you would expect tertiary better than secondary better than primary better than ammonia
however this is not the case. it also depends on SOLUBILITY
tertiary amines are less soluble in water so they are less strong bases. aromatic amines (counted above as part of primary) are terrible bases because LP on N is delocalised into benzene ring so not available.
real trend is:
Secondary > tertiary > primary > NH3 > aromatic amines
Why could you make a buffer using amines
How could you
Buffers are made of weak acids and limited strong base/salt of weak acid
OR weak base and limited strong acid/salt of weak base
Amines are weak bases therefore could make buffer using them. You could have the amine and the quaternary ammonium salt
Use of aliphatic amines
Make N substituted amides when react with acyl chlorides or acid anhydrides
Mech: nucleophilic addition elimination
How do you name N substituted amides
__yl __amide
Functional group of amides is
O H
|| |
RC — NR
1st space is for the R on the N. Secondary amides are when you use the N; named by using an N to indicate that an alkyl group is attached to the nitrogen atom.
We normally see secondary amides. A primary would have 2 Hs on it: the one in F group and thr R would be a H
2nd space is for the C chain including the C in carbonyl group
